Block copolymers are polymers having two or more distinct polymeric units, or “blocks”. Such polymers are useful in a variety of different applications, and it is particularly preferred to be able to produce block copolymers having polyester and polycarbonate blocks.
Block copolymers can be produced in a variety of different ways. For example, the individual blocks may be prepared separately, and then joined together. Alternatively, a first block, comprising an initiating moiety (also known as a “macroinitiator”) can be added to a mixture of one or monomers, and the second block is grown from the end of the pre-formed block. However, such methods require the formation and purification of the first blocks prior to the formation of a second block, and generally involve the use of different catalytic systems to produce each block. These methods can therefore be costly and difficult to use.
The inventors have surprisingly found that it is possible to produce block copolymers comprising two or more blocks, using a single catalytic system, either by the subsequent addition of monomer, or by a “one-pot” method in which all of the monomers are present in the reaction mixture at the start of the reaction.